1. Field of the Invention
The present invention relates to a conveyor chain for a transporting plant in which each chain link made of a synthetic material includes a plate for supporting the material to be conveyed, a head piece provided with a cylindrical bore and a yoke-shaped portion with two legs extending from the head piece. For cardanically coupling two chain links, a bolt rotatably inserted in the cylindrical bore of the head piece is provided with a transverse bore and the legs of the chain link are provided with bores in alignment with the transverse bore, wherein a metal connecting pin is inserted into the transverse bore of one chain link and in the bores of the legs of the preceding chain link in travel direction.
2. Description of the Related Art
A conveyor chain of the above-described type is known from DE 32 35 224 C2. In the assembled state, the plates supporting the material to be conveyed are at the top. The front and rear transverse edges in conveying direction are provided with teeth, wherein the teeth are offset relative to each other, so that the teeth of the rear transverse edge engage in the tooth gaps of the front transverse edge of the next following chain link. These types of conveyor chains have the advantage that they can be guided in a horizontal plane as well as about a horizontal axis. The deflection in a horizontal plane is made possible by a bolt inserted in the bore of the head piece. The deflection about a horizontal axis is made possible by the connecting pin which couples the chain links.
In conveyor chains of the above-described type, each plate forms together with the head piece and the yoke-shaped portion a single structural component which is made of synthetic material. Because of its elasticity, the conveyor chain is expanded to a relatively significant extent. This expansion causes an unfavorable dynamic behavior, so that the travel of the chain is not smooth which is called the stick-slip effect in the art of conveyor chains. Moreover, the drive situation is no longer exactly definable. The fact that the travel is not smooth has a negative effect on the positioning of the material being conveyed and, thus, the operational safety of the transporting plant. The conveyor chain is usually driven by means of chain wheels over which the conveyor chain is guided. These chain wheels engage with the connecting pin. The non-rotatable support results in unfavorable engagement conditions, so that the wear of the chain wheel and of the conveyor chain is increased. Consequently, the operational safety and the service life of the conveyor chain are reduced.